Endoscope light source apparatus with a light emitting timing delaying circuit

ABSTRACT

A white light of a lamp which can flash is passed through a rotary filter fitted with a plurality of color filters to output colored lights of a field sequential type. An output signal of a color filter detecting device, detecting the timing when the color filters are interposed in a light path, is used to produce trigger signals different in the delay amount. The light emitting timing of the lamp is delayed relatively from the time when the color filters are interposed in the light path to control the emitted light amounts of the colored lights.

BACKGROUND OF THE INVENTION: Field of the Invention and Related ArtStatement

This invention relates to an endoscope light source apparatus providedwith a means of controlling an illuminating light amount to an object tobe imaged.

In an endoscopic observation, an exclusive light source apparatus isused so that an illuminating light from the light source apparatus maybe radiated onto an object to be imaged from a tip of an endoscopethrough light guide fibers within the endoscope. In order to adjust theilluminating light amount in response to the brightness (reflectionfactor) of the object to be imaged, a diaphragm blade is providedbetween a connector with the endoscope and a lamp within the lightsource apparatus. A slitted plate or honeycomb plate provided rotatablywith the axis intersecting at right angles with a light path as a centeris used for such a diaphragm blade. That is to say, by electrically ormechanically rotating this diaphragm blade, the light intercepting ratecan be varied to adjust the light amount incident upon the light guide.A related art example using a honeycomb diaphragm is mentioned in aJapanese patent application No. 173832/1984.

The endoscope light source apparatus of the above mentioned related artexample shall be explained with reference to FIG. 1. Here, a so-calledelectronscope in which a solid state imagining device is built withinthe tip part of an insertable part to image an object shall beexplained. A light source apparatus 102 is connected to an electronscope100. The electronscope 100 is provided with a light guide 106 consistingof an optical fiber bundle leading an illuminating light radiated fromthe light source apparatus to the tip of the insertable part toilluminate an object 104 and a charge coupled device (CCD) 108 as asolid state imaging device built within the tip part.

The light source apparatus 102 is provided with a light source such as,for example, a lamp (xenone lamp) 110. The lamp 110 is regulated to beof a constant current so that, when an output signal of a pulsegenerating circuit 172 is input into a current regulating circuit 114, aflash will be emitted as synchronized with the signal. A switchingcircuit 116 is connected to the current regulating circuit 114 to form alight source lighting circuit 118.

The light emitted from the lamp 110 is incident upon the light guide 106of the electronscope 100 through a diaphragm blade 120, optical lenssystem 122 and rotary filter 124. The diaphragm blade 120 is rotated bya driving device 126 and consists of a slitted plate or honeycomb platevariable in the inclination with the light path. The rotary filter 124is rotated by a motor 128 and colors the illuminating light in red(R),green (G) adn blue (B) in turn. There is a light intercepting periodbetween the exposure periods of the respective color components. Anoptical sensor 130, detecting the exposure periods of the respectivecolor components of the rotary filter 124, is provided. When theexposure periods of the respective color components end, a pulse will beoutput from the optical sensor 130 and will be fed to a color signalsynchronizing circuit 132. After a predetermined period (correspondingto the light intercepting period) from this synchronizing pulse, onlyfor a fixed period (corresponding to the exposure period), the colorsignal syncrhonizing circuit 132 feeds a color synchronizing signal tothe pulse generating circuit 112 so that the lamp 110 may besynchronized with the rotation of the rotary filter 124 and may emit alight only in the exposure periods of the respective colors.

The output signal of the CCD 108 is fed to the light source device 102side through a signal line and connector 138 within the electronscope100 and is input into a signal processing circuit 140 making anamplification, clamping and various corrections. The output of thesignal processing circuit 140 is fed to a video circuit 142 and apicture image is output in a displaying part (not illustrated). Theoutput of the signal processing circuit 140 is input also into adifferential amplifier 144. The standard signal of the differentialamplifier is given by a standard voltage circuit 146. The output of thedifferential amplifier 144 regulates the diaphragm driving device 126.

An integrator is also provided within the signal processing circuit sothat the illuminating light amount may be detected. The differencebetween this light amount value and the standard signal is operated bythe differential amplifier 144. In response to this result, thediaphragm driving device 126 is regulated. Thereby, the diaphragm blade120 will be inclined in the direction of intercepting the light in casethe illuminating light is too bright and will be inclined in thedirection of opening the light path in case the illuminating light istoo dark. This automatic light adjusting operation is the same not onlyin an electronscope but also in an ordinary fiberscope.

In a conventional light source apparatus for endoscopes, the diaphragmblade is exclusively for adjusting the light, the driving mechanism isfor rotating the diaphragm blade and their control circuit areseparately required. Therefore, defects have caused the number of thecomponent parts to increase and has caused the light source apparatus tobecome large, complicated and costly.

Now, in an electronic endoscope apparatus using a field sequentialsystem, in order to improve the color reproductivity of an endoscopepicture image, it is necessary to adjust the color balance (whitebalance) of R, G and B in advance. In the case of using, for example, asa prior art example, the rotary filter 2 provided with respective R, Gand B color transmitting filters 1R, 1G and 1B as shown in FIG. 2 for alight source emitting a continuous light, there is used a method ofadjusting the aperture ratio of the respective R, G and B colortransmitting filters 1R, 1G and 1B by using the light interceptingmember 3. Even if the aperture rates of the respective R, G and B colortransmitting filters 1R, 1G and 1B are set in advance, depending on thedispersion of the imaging device or the like, it can not be said thatthe best state can always be held. In such a case, a light interceptingmember is further added to the aperture surface of the filter set inadvance.

In this prior art example, even if the aperture rates of the respectivecolor transmitting filters are set in advance, due to the dispersion ofthe imaging device or the like, the aperture rates of the respectivecolor filters must be readjusted by using a light intercepting member.In such a case, defects occur where no accurate color balance adjustmentcan be made, a light intercepting member is required and a large amountof time is needed for the adjustment.

When a flash light source is used (which shall be referred to as astrobo lamp hereinafter), and when the energy fed to the strobo lamp ismade variable, the emitted light amount can be adjusted. Therefore, whenproper energy is fed to the strobo lamp to emit a light within theaperture time of the respective R, G and B color filters as shown inFIG. 3a, the R, G and B color balance can be adjsuted the same as in theabove mentioned example.

In order to make the fed energy variable, there is adopted a methodwherein the number of times of the strobe light emission is madevariable during the aperture time of the respective color filters ismade variable is made variable.

In the method wherein the number of times of the light emission of thestrobo lamp during the aperture periods of the respective color filtersis thus controlled, it is necessary to expand the control range byincreasing the number of times of the light emission of the strobo lampwhich therefore causes a defect in that the life of the strobo lamp isextremely reduced.

Also, as disclosed in a Japanese patent laid open No. 205884/1984 (orU.S. Pat. No. 4,532,918), there is adopted a method wherein thecondenser capacity, represented by the formula of Energy E=1/2 CV², andthe applied voltage V are adjusted.

In this prior art example, the energy fed to the strobo lamp must bemade variable during the aperture time of the respective R, G and Bcolors which therefore causes defects in that the control circuit iscomplicated and costly.

Objects and Summary of the Invention

An object of the present invention is to provide an endoscope lightsource apparatus wherein the emitted light amount of a flash emittinglamp can be adjusted with a simple formation.

Another object of the present invention is to provide an endoscope lightsource apparatus wherein colors can be balanced at a high precision witha simple formation.

The present invention is provided with a light source lamp emitting aflash, a lighting circuit of this light source lamp, a color wheelprovided with a plurality of color filters coloring the white light ofthis light source lamp and a device for detecting the positions of colorfilters interposed in a light path so that, by controlling the lightemitting timing of the light source lamp for the time when the colorfilters are interposed in the light path, the emitted light amounts ofthe respective colored lights can be varied with a simple formation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a light source apparatus of the first priorart example.

FIG. 2 is a view showing a rotary filter used in the second prior artexample.

FIG. 3 shows operation explaining diagrams of the third prior artexample.

FIG. 4 is a schematic diagram of a light source apparatus of the firstembodiment of the present invention.

FIG. 5 is a block diagram showing a detailed formation of the firstembodiment.

FIGS. 6a-6f are timing charts showing the operation of the firstembodiment.

FIG. 7 is a block diagram of an essential part of the second embodimentof the present invention.

FIGS. 8 to 11 relate to the third embodiment of the present invention.

FIG. 8 is a formation diagram of an electronic endoscope apparatusprovided with the third embodiment.

FIGS. 9(a)-(g) are an operation explaining view of the first embodiment.

FIG. 10 is a formation diagram showing a concrete formation of the firstembodiment.

FIGS. 11(a)-(i) are timing charts for explaining the operation of thefirst embodiment.

FIG. 12 is a formation diagram of the fourth embodiment of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 4 is a schematic diagram of the first embodiment. The samereference numerals are attached to the same parts as in the prior artexample in FIG. 1. The difference from the prior art example is that adelaying circuit 150 is provided between the differential amplifier 144and pulse generating circuit 112 without providing a diaphragm blade anddiaphragm driving device. For the convenience of explanation, here thesignal processing circuit 140 and differential amplifier 144 arecombined to be a light adjusting signal generating circuit 152.

FIG. 5 shows the details of the delaying circuit 150 and light adjustingsignal generating circuit 152 of the first embodiment. The output of theCCD 108 is input into the signal processing circuit 140. The output ofthe signal processing circuit 140 is fed to the integrator 154consisting of a switch S1, resistance R1 and capacitor C1. The switch S1is controlled to open and close by the control circuit 156. The outputof the integrator 154 is fed to the differential amplifier 144.

The delaying circuit 150 comprises a voltage controlling resistor (VCR)158 and a monostable multivibrator 160. The VCR 158 varies theresistance value with the applied voltage. The output of thedifferential amplifier 144 is applied to the VCR 158. The VCR 158becomes a resistance determining the time constant of the monostablemultivibrator 160. The output of the color signal synchronizing circuit132 is input into the monostable multivibrator 160 and the output of themonostable multivibrator 160 is fed to the pulse generating circuit 112.

The operation of the first embodiment shall be explained in thefollowing with reference to the timing charts shown in FIGS. 6a to 6f.With the rotation of the rotary filter 124, a color synchronizing signalsuch as is shown in FIG. 6a will be output from the color signalsynchronizing circuit 132. The filtering manner by the rotary filter 124is shown in FIG. 6b. The exposure period is represented by t1 and thelight intercepting period is represented by t2. That is to say, when theexposure of the respective colors ends, a color synchronizing signalwill be output. The color synchronizing signal triggers the monostablemultivibrator 160 but, in this embodiment, the time constant of themonostable multivibrator 160 is determined by the VCR 158 varying theresistance value with the output of the light adjusting signalgenerating circuit. After the monostable multivibrator 160 is triggeredand the time of the time constant passes, the output rises to output apulse of a fixed width. The resistance value of the VCR 158 willincrease when the light adjusting signal increases but will decreasewhen it decreases. Therefore, the delayed time of the delaying circuit150 will also increase when the light adjusting signal increases butwill decrease when it decreases.

It is assumed that the brightness of an object to be imaged varies frombeing medium to being small and from being small to being large. Theoutput video signal of the CCD 108 then is shown in FIG. 6c. This videosignal is integrated by the integrator 154 and the integrated value perframe is held by the capacitor C1. This integrated output is shown inFIG. 6d. The integrated output is fed to one input terminal of thedifferential amplifier 144. The standard signal fed to the other inputterminal of the differential amplifier 144 is shown by the broken linein the same diagram. The difference between the standard signal andintegrated signal is applied as a light adjusting signal to the VCR 158as a control voltage. That is to say, the larger the brightness of theobject to be imaged, the larger the delayed time of the delaying circuit150.

Thus, the delayed signal delayed by T in response to the brightness ofthe object from the color synchronizing signal (in FIG. 6a) is fed tothe pulse generating circuit 112 from the monostable multivibrator 160.The delayed signal is shown in FIG. 6e. During the period t3 in whichthis delayed signal is being generated, the pulse generating circuit 112will flash the lamp 110 through the light source lighting device 118.Here, when the brightness of the object is medium or large, before theflashing period t3 ends, the light intercepting period t2 of the rotaryfilter will start and therefore the later half of the emitted light willbe intercepted as shown in FIG. 6f. Therefore, the emitted light amountof the lamp 110 incident upon the light guide 106 will reduce to besmaller then when the brightness of the object is small. Therefore, evenif no diaphragm is used, the light will be able to be automaticallyadjusted.

The following relations are necessary among the flashing period t3,exposure period t1 and light intercepting period t2.

    t3<t2                                                      (1)

    t1+t2>T+t3                                                 (2)

As explained above, according to this embodiment, there can be realizedan endoscope light source apparatus wherein, by delaying the flashingstarting timing of the lamp to be later than the exposure startingtiming of the rotary filter in response to the light adjusting signal,the light can be automatically adjusted with a simple formation withoutusing the diaphragm blade.

Since the light adjusting signal is determined on the basis of thedifference between the integrated output and standard signal, the lightcan be adjusted to be of any desired brightness by varying the voltageof the standard signal.

The second embodiment of this invention shall be explained in thefollowing. FIG. 7 is a block diagram of an essential part of the secondembodiment. The second embodiment is different from the first embodimentonly in the formation of the delaying circuit 150 but is the sameotherwise. That is to say, the output of the differential amplifier 144is input into an A/D converter 170. The A/D converter 170 converts theA/D by a sampling pulse from the control circuit 156, makes only theoutput of any of 1 to n effective and conducts only the correspondinganalogue switch in the analogue switch circuit 172. Thereby, any one ofexternal resistances Rx1 to Rxn is selected and is connected to the timeconstant circuit of the monostable multivibrator 160 and the timeconstant is determined by Rx and Cx. Therefore, also in the secondembodiment, as the delaying circuit 150 feeds a delayed signal delayedfrom the color synchronizing signal to the pulse generating circuit inresponse to the light adjusting signal, the flashing start of the lamp110 will be delayed and the light will be automatically adjusted.

This invention is not limited to the above described embodiment and canbe variously modified. The lamp 110 may be any flashable lamps such as adirect current arc discharge lamp and strobo lamp. This flashing meansthat the light amount can be increased or decreased by the increase ordecrease of the lamp current. The light need not always be extingushedduring the light intercepting period. Further, the delayed time of thedelaying circuit 150 can be manually adjusted not by the light adjustingsignal and the light may be adjusted manually not automatically. Thelight source for electronscopes has been explained but can be appliedalso to a light source for fiberscopes wherein a television camera isfitted to an eyepiece part.

As explained above, according to the first and second embodiments, therecan be realized an endoscope light source apparatus of a simpleformation requiring neither mechanical diaphragm blade nor diaphragmdriving device. Thus, the number of the component parts is reduced, theapparatus can be made small and the price can be made low.

As shown in FIG. 8, an electronic endoscope apparatus 11 provided withthe third embodiment comprises an electronic endoscope 13 having aninsertable part 12 elongated so as to be insertable into a body cavityor the like, a video processor 14 into which the signal imaged by thiselectronic endoscope 13 is to be input and a color monitor 15color-displaying the video signal processed by this video processor 14.

A (video) processing circuit 16 processing the signal, a light sourceapparatus 17 feeding an illuminating light and a color balance adjustingpart 18 are built within the above mentioned video processor 14.

A light guide 21 transmitting the illuminating light is inserted throughthe insertable part 12 of the above mentioned electronic endoscope sothat the illuminating light fed from the light source part 17 to theentrance end may be transmitted to be emitted from the exit end and anobject 23 to be imaged may be illuminated by the illuminating lightexpanded through a light distributing lens 22.

The illuminated object 23 is imaged on the imaging surface of a CCD 25by an objective lens 24. When a driving signal output from a driver 26is applied, the CCD 25 will output a photoelectrically converted signal.This signal is amplified by an amplifier 27 and is then input into theprocessing circuit 16 within the video processor 14 through a signalcable 28. The signal is processed by this processing circuit 16 toproduce an NTSC compound video signal which is color-displayed by thecolor monitor 15.

The above mentioned light source apparatus 17 within the above mentionedvideo processor 14 is of a field sequential type. The white light of alight source lamp 31 is made a parallel beam by a collimator lens 32. Arotary filter 34 rotated and driven by a motor 33 is interposed on alight path made by this parallel beam. The light passed through thisrotary filter 34 is further condensed by a condenser lens 35 and isradiated onto the entrance end surface of the light guide 21.

In the above mentioned rotary filter 34, as shown in FIG. 10, threesector apertures are formed in a disc frame and color transmittingfilters 34R, 34G and 34B transmitting respectively red, green and bluecolors are fitted in the respective apertures. When the rotary filter 34is rotated and driven, these color (transmitting) filters 34R, 34G and34B will be interposed and retreated sequentially in the course of thelight path. The time when the respective color filters 34R, 34G and 34Bare interposed on the light path is mentioned as the aperture time ofthe filter.

When the above mentioned color filters 34R, 34G and 34B are interposedsequentially on the light path, the lights, that is, the red, green andblue illuminating lights having passed through these color filters 34R,34G and 34B, will be fed sequentially onto the entrance end surface ofthe light guide 21. Therefore, the object 23 is illuminated sequentiallyby the lights of wavelengths of red, green and blue. The signal imagedunder this field sequential illuminating state is input into theprocessing circuit 16.

Now, the motor 33, to make the above mentioned field sequentialillumination, is controlled by the rotation controlling signal outputfrom a motor controlling circuit 36 so that its rotating speed may beconstant. A standard clock signal CLK output from a standard signalgenerating circuit 37 is input into this motor controlling circuit 36 toproduce a rotation controlling signal synchronized with this standardclock signal CLK. As the motor 33 is synchronized with the standardclock signal CLK and is controlled to be at a constant speed, as shownin FIG. 9b, the aperture time when the respective color filters 34R, 34Gand 34B are interposed on the light path will be also synchronized withthe standard clock signal CLK in FIG. 9a. The above mentioned standardsignal generating circuit 37 outputs the standard clock signal CLK alsoto a timing controlling circuit 38. This timing controlling circuit 38outputs a light emitting timing signal such as is shown in FIG. 9c to alighting device 39 lighting the light source lamp 31 to control thelight emitting time of the light source lamp 31.

By the above mentioned light emitting timing signal, the light emittingtime of the light source lamp 31 is controlled and, by the relationbetween this light emitting time and the filter aperture time, the fedlight amount (emitted light amount) fed actually to the light guide 21is variably controlled and the color balance is adjusted.

That is to say, when the light emitting timing signal is made tocoincide with the aperture time of the filter, the timing when the colorfilters 34R, 34G and 34B are interposed on the light path and the timingwhen the light source lamp 31 emits the light will coincide with eachother and therefore the emitted light amount to the light guide 21 willbecome large. On the other hand, when the light emitting timing time isdisplaced as shown in FIG. 9c from this filter aperture time, as shownin FIG. 9d, the light emitting time will be displaced and the lightemitting waveform will be also displaced. Only for the light emittingperiod overlapping the aperture time, the output light will be fedactually to the light guide 21. This output light period is shown inFIG. 9c.

Thus, the timing of outputting the light emitting timing signal iscontrolled and the emitted light amount to the light guide is variablycontrolled to adjust the color balance.

The operation of the embodiment in FIG. 7 shall be explained in thefollowing with reference to FIG. 9.

As in FIG. 9a, a standard clock signal is oscillated by the standardsignal generating circuit 37 and is input into the motor controllingcircuit 36 and timing controlling circuit 38. The rotary filter 34fitted to the motor 33 is controlled to rotate at a constant speed bythe motor controlling circuit 36 by the signal synchronized with thestandard clock signal. Therefore, as in FIG. 9b, the aperture time andtiming of the respective color filters synchronized with the standardclock signal are determined. Here, T1 represents the aperture time ofR(red), T2 represents the aperture time of G(green) and T3 representsthe aperture time of B(blue). As in FIG. 9c, a light emitting timingsignal synchronized with the standard clock signal, the same as in theabove mentioned aperture time, is output from the timing controllingcircuit 38. Signals delayed by the time t1 for the rise of the aperturetime of R, by the time t2 for the rise of the aperture time of G and bythe time t3 for the rise of the aperture time of B are shown to beoutput. The signal shown in FIG. 9c is input into a lighting device 39for lighting and controlling the light source lamp 31. The light sourcelamp 31 emits a light as synchronized with the above mentioned lightemitting timing signal. FIGS. 9d and 9e are of examples of controllingthe current fed to a continuously lighted lamp such as a direct currentarc discharge lamp. The output light output on a low level shows aresidual light. In this example, the current of the lamp is controlledas synchronized with the light emitting timing signal to control theemitted light.

As shown in FIG. 9, as the light source emits a light (the light amountincreases) as delayed by the time t1 (or t2 or t3) for the timing of thefilter aperture time T1 (or T2 or T3), the light emission will continueto the light intercepting period of the rotary filter 34. That is tosay, if the filter aperture time and the light emitting timing aresimultaneous without delay, the emitted light will be all emitted duringthe period of tR (or tG or tB) and the light amount will be 100% outputlight but, if a delayed time of t1 (or t2 or t3) is provided, theemitted light will be delayed by the time of t1(or t2 or t3) and thelight will become darker by the emitted light for the time of t1 (or t2or t3) than in the state of 100%. In the present application, the colorbalance is adjusted by utilizing this point. When the above mentionedtime t1, t2, and t3 are independently freely controlled, the amount ofthe emitted light colored in the respective colors will be varied andtherefore the color balance can be adjusted very simply and accurately.For example, after the time t1, t2 and t3 are set to be optimum, if thetime t1, t2 and t3 are varied at the same ratio so as to follow thebrightness level of the video signal, the light can be adjusted.

FIGS. 9f and 9g are of examples of using a strobo lamp. The differencein this case is the difference of the light emitting system of the lightsource lamp 31.

The above mentioned direct current arc discharge lamp has acharacteristic that it can not be lighted just after it is extinguished.Therefore, the lamp current is increased or decreased to emit a light assynchronized with the light emitting timing. In such a case, a residuallight shown in FIG. 9e will be generated. On the other hand, in thestrobo lamp, there are advantages that the light can be perfectly set onand off, can be therefore continuously emitted within a short time, theflashing time is also short, therefore the imaging time is short and asharper image is obtained.

FIG. 10 shows a concrete formation of the third embodiment.

The standard signal generating circuit 37 outputs a standard clocksignal to the motor controlling 36 and timing controlling circuit 38.The motor controlling circuit 36 outputs a driving signal to the motor33 for rotating the rotary filter 34. In this embodiment, the rotaryfilter 34 is controlled to rotate at a constant speed as synchronizedwith the standard clock signal.

The timing controlling circuit 38, into which the above mentionedstandard clock signal is input, is formed of a counter 41 counting thestandard clock signal output from the standard signal generating circuit37, an R (red) delaying circuit 42R, G (green) delaying circuit 42G andB (blue) delaying circuit 42B for receiving a signal output at aconstant timing from the counter 41 and generating a light emittingtiming signal having any delayed time and a three-input gate circuit 43into which the outputs of these delaying circuits 42R, 42G and 42B arerespectively input.

The output of the above mentioned gate circuit 43 is input into alighting circuit 45 through an emitted light amount variable circuit 44forming a lighting device 39 and controls the lighting of the lightsource lamp 31.

The above mentioned delaying circuit 42R, 42G and 42B are formedrespectively, for example, of monostable multivibrators (which shall bementioned as MSM hereinafter) and are connected respectively withresistances Ri and condensers Ci (i=1, 2 and 3) to respectivelydetermine the delayed time t1, t2 and t3. For example, in case 74LS221of a transistor-transistor logic (TTL) is used, the delayed time can beset by ti=0.7RiCi.

In case the above mentioned TTL is used, the counter 41 will output apulse signal which will become "H" at substantially the same timing asthe timing at which the color filter 34R opens to the input terminal Bof the MSM 42R (See FIG. 11c) and the MSM 42R will output a pulse whichwill become "L" for the time t1 from the reverse output terminal Q ofthe MSM 42R as shown in FIG. 11f at its rising and will then return to"H".

In the same manner, the counter 41 will output to the MSM 42G is pulsesignal which will become "H" at substantially the same timing as thetiming at which the color filter 34G opens (See FIG. 11d) and the MSM42G will output a pulse which will become "L" for the time t2 from itsreverse output terminal Q as shown in FIG. 11g at the rising edge atwhich the output of the counter 41 becomes "H" and then will return to"H". In the same manner, the MSM 42b will output a pulse which willbecome "L" for the time t3 from its reverse output terminal Q at therising edge at which the output of the counter 41 becomes "H" and thenwill return to "H" (See FIG. 11h). Therefore, the gate circuit 43outputs a light emitting timing signal (See FIG. 11i) taking the logicalproduct of them. This timing signal is somewhat different from thetiming signal shown in FIG. 9 but is equal with respect to the outputlight emitted onto the light guide 21 through the rotary filter 34. Thatis to say, the light emitting timing signal as the output of the gatecircuit 43 is transmitted to the lighting device 39 through the emittedlight amount variable circuit 44 within the lighting device 39 and tothe light source lamp 31 through the lighting circuit 45 to emit a lightfor the period when the light emitting timing signal is "H".

The output light having passed through the rotary filter 34 becomes asin FIGS. 9e and 9g.

According to this embodiment, by adjusting the values of Ri and Ci whichare constants to determine the delayed time t1, t2 and t3 of thedelaying circuits 42R, 42G and 42B, respectively, the emitted lightamount fed to the light guide 21 through the respective color filterscan be adjusted and therefore the electronic endoscope can be set in thebest color balanced state easily at a high precision.

FIG. 12 shows a light source apparatus having a color balance adjustingmeans of the fourth embodiment of the present invention.

This embodiment is the same as the embodiment shown in FIG. 10 exceptthat a sensor 51 for sensing the rotating speed of the rotary filter 34and a waveform shaping circuit 52 for shaping the waveform of a signaloutput from this sensor 51 and inputting the signal into the counter 41are newly provided. The standard signal generating circuit 37 is deletedin the embodiment shown in FIG. 10.

The above mentioned sensor 51 comprises a light emitting device andlight receiving device 51a arranged to hold a filter frame, for example,of the rotary filter 37 so that a light pulse, in case the lightreceiving device 51a receives the light of the light emitting devicethrough holes 34a provided at regular intervals in the peripheraldirection of the filter frame, may be photoelectrically converted andled to the waveform shaping circuit 52.

The motor 33 fitted with the rotary filter 34 rotates at a constantspeed by the motor controlling circuit 36. The sensor 51, sensing therotating speed of the rotary filter 34, is provided in a proper positionon the periphery of the rotary filter 34 so that the signal obtainedfrom the sensor 51 may have the waveform shaped by the waveform shapingcircuit 52. This signal operates as a standard clock signal as in FIG.9a or 11d.

The operation of this embodiment shall be explained in the following.

A standard clock signal obtained by the above mentioned waveform shapingcircuit 52 is counted by the counter 41, is synchronized with theaperture time of the filter and is fed to the respective delayingcircuits 42R, 42G and 42B. Therefore, a light emitting timing signal,having the delayed time t1, t2 and t3 set by the constants Ri and Ciprovided in the respective delaying circuits, is fed to the lightingdevice 39 as in FIG. 9c or 11i. Therefore, the same as in the thirdembodiment, the emitted light amount passing through the respectivecolor filters can be freely adjusted and therefore the color balance canbe adjusted.

In this embodiment, even when the speed of the rotary filter 34 isunstable, as the rotating speed is always sensed and the light emittingtiming signal is output, the color balance can be adjusted moreaccurately.

A means of detecting the positions of the respective color filtersinterposed on the light path may be provided and the light may beextinguished except at the aperture time.

The above mentioned respective embodiments have a feature that thecolors can be balanced irrespective of the kind of the light sourcelamp.

The emitted light amount can be also controlled by emitting, as pulses,the emitted light amounts of the R, G and B lamps.

As described above, according to the third and fourth embodiments, asthe lighting of the light source lamp is controlled through the delayingmeans synchronized with the time when the respective color filters ofthe rotary filter are interposed, the color balance can be adjusted at ahigh precision with a simple formation.

What is claimed is:
 1. An endoscope light source apparatus for feedingan illuminating light to an endoscope comprising:a lamp capable offlashing; a lighting circuit feeding electric power to said lamp; arotary filter interposed in a light path of a color developing light ofsaid lamp and fitted with respectively different color transmittingfilters in a plurality of aperture windows provided in a lightintercepting plate; a rotating driving means rotating said rotaryfilter; a color filter detecting means detecting the color transmittingfilters interposed in said light path and outputting a detecting signal;and a light emitting timing delaying means outputting into said lightingcircuit a trigger signal delayed by using the detecting signal of saidcolor filter detecting means.
 2. An endoscope light source apparatusaccording to claim 1 wherein said light emitting timing delaying meanscan be set at delay amounts different for said respective colortransmitting filters.
 3. An endoscope light source apparatus accordingto claim 1 wherein said light emitting timing delaying means is formedof a monostable multivibrator which can be set at different delayamounts in response to said color transmitting filters.
 4. An endoscopelight source apparatus according to any of claims 1 to 3 wherein saidrotating driving means comprises a motor rotating and driving saidrotary filter and a motor controlling means keeping the rotating speedof said motor constant.
 5. An endoscope light source apparatus forfeeding an illuminating light to an endoscope comprising:a lamp capableof flashing; a lighting circuit feeding electric power to said lamp; arotary filter interposed in a light path of a color developing light ofsaid lamp and fitted with respectively different color transmittingfilters in a plurality of aperture windows provided in a lightintercepting plate; a rotating driving means rotating said rotaryfilter; a color filter detecting means detecting the color transmittingfilters interposed in said light path and outputting a detecting signal;and a light emitting timing delaying means outputting into said lightingcircuit a delayed trigger signal from a video signal of an imaging meansforming the endoscope and the detecting signal of said color filterdetecting means.
 6. An endoscope light source apparatus according to anyof claims 1 or 5 wherein said light emitting timing delaying meansoutputs a trigger signal of a delay amount different in the lightemitting timing in response to a time series color signal level forminga video signal.
 7. An endoscope light source apparatus according toclaim 6 wherein said timing signal delaying means comprises anintegrating circuit integrating said color signal to produce an averagevalue for one frame, a differential amplifier comparing the averagevalue level of said integrating circuit with a standard voltage leveland outputting a difference signal between them and a variable delayingcircuit outputting a trigger signal different in the delay amount fromthe timing of the detecting signal of said color filter detecting meansby the output signal level of said differential amplifier.